Alloy steel



Patented Sept. 1 '19 25,

UNITED STATES rem PATEN emu.

may '1'. manna, or nn'rnorr, moment.

no mun proved Alloy Steel, of which the followis a specification. V v

e present invention has reference to new alloy steels, its object being to provide a heat treated steel or alloy steel which possesses physical properties and" combinations of properties of a relatively high order as compared with the best practice 1n steels heretofore. Certain forms of these steels are especially adapted for armor plate, but the steels may be used for other 1purposes, in fact, they may be advantageous y substituted generally for those steels or steel alloys wherein high values of static or dynamic physical properties or combinations of these" properties enter as determining factors In these new steels, these properties are not only in themselves of the highest order, but there may be associated with them b suitable heat treatment a hi h degree 0 hardness as measured by the lZrinell, sclerescope. and, scratch tests which renders the steel particularly suitable for armor plate, prol iqielgtiles and guns, and also gears and the e. 4 Z The nature and objects of my invention maybe exemplified b consideringits application to armor p ate, for the requirements and service to he met by such material is such that only the best products of the steel makers art can be used, and, obviously a new steel which meets the require-E ments of this particular class'of service will also, with modifications apparent to those skilled in the art, -'be of value in general application for other uses such asctoolsy dies. and other machine parts insome'jof which the question of extreme toughness, rather than toughness withextreme hardness, ismore nearly controlling. I

Due to the recent developments of ammunition and methods of warfare,

service requirements of armor platehave so increased that they can be metgenerally Kbnly by the best high dutyj ideal qumng su and combin tions' of such properties, the

manganese-nickel-vanadium steels, are sub jectile, while a softtou' fi esse Tap of the metal required ttgjwithstand the pro-.,

Application and sum 10, mo. semi I slam conditions of manufacture heat treat- 7.

ment; and for some purp0sesas in the case of a suitable protection 'for the vital parts of an aeroplane and in bod armor, for ex ample-where weight may determiningl factor, cannotbe met satisfactorily at- Under these conditioners- '-excellent physical properties various alloy steels generally employed for this purpose, namely, the nickel steels, the nickel chromium steels and the silico-manganese steels as well as the later developed nickel-chromiumcobalt, molybdenum and ject to a high percentage .of'loss both in the process of manufacture and on ballistic test, which has been with the best manufacturin practice heretofore seldom under 15% and usually from 30% to 60%. In'other words, they are sensitiveftothevarious steps involved in their manufacture, particularly in the matter of heat treatment, the result be-' ing that plates produced in substantially the 7 same way, withmthe limits of mauufacturin? practice, often difier sufiicientl from 0t ers to be rejected. This is particularly true in the casepf thin sheets, which are generally used for mobile instruments.

The capabili of a steel to resist the iniso "pact of rojecti es is dependent upon a variv e'ty of e ements' among which hardness and toughness stand out. Thesetwo properties may be regarded as antagonistic to each other, in-other words; steels possessing a high degree of hardness, either Sclerescope or Brinell, are not ordinarily tough and those unusually tough are of the softer des; For exampl'e,-a plate of extreme ardn'ess becomes brittle and cracks or so breaks upon receiving the imlpact of the pro 7 p ate is-too read- 112 pierced. To proper y resist, the'impact' '0 t be so hard as to the former and thus as read its blow ova. aconsiderable area, for without this shatte ggaetidn the thickness jectile provestoo I a uses. in addition, .a-

of toughness-, -of 100 said to he the 55' e projectile the face of the plate must ing if below.

which high breaking strength, increased elongation and high reduction in area belore breaking are evidence, is necessary, as the entire energy of the blow must be absorbed by the plate Without it cracking or punching throu h.

The best stee s heretofore employed for armor plate, even when carbonized or surface hardened, have for any given service a very narrow range of hardness within which they possess the required toughness, and departures from these limits have led to cracking and breaking if above or pierc- This hardness is dependent upon heat treatment, and the latter, being difiicult to control accurately, is largely responsible for the high ballistic loss.

Because of the non-uniformity of product, in so far as its suitability for use as armor plate is concerned, resulting lrom present practice, it is customary to submit each plate (u to a thickness of substantially ,6 of an inc and representative samples of thicker material) to a firing or ballistic test, which consists in firing, with a standard rifle or machine gun, bullets of the regular or off the armor piercing type at predetermined ranges and velocities, depending upon the service for which the plate is intended. Such plates as withstand the impact of the projectiles without breaking, cracking or undue deitormation are accepted as satisfactopy, while those pierced, cracked or broken are rejected. F or example, a satisfactory plate, .615 inches in thickness should, under present testing practice, withstand at a range of 50 yards, five shots, within the area of a live inch circle, fired from a standard machine gun calibre 30 with armor piercing bullets havin a muzzle velocity of 2800 feet per second.

%he usual steels have also proven, for the most part, difiicult to manipulate in one or more of the melting, casting, heat treatment and forming o erations necessary in their manufacture. either "has it been possible to produce a steel of appreciably less thickness and capable of withstanding the test outlined above.

'lorecapitulate: The determining factors in the production of satisfactory, armor plate are- 1. Ability to withstand bullets or other projectiles without penetration or fracture, that is, high ballistic yield. I

2. Weig t, which is, of course, a prime consideration needing no explanation.

3. Ease of manufacture under' present steel making methods.

4. Cost, which materially enters into-the three above named considerations; and these same factors enter to a eater or lessdegree into the production ofiigh class steels for use generally in various arts of which the automotive and machine building industries are good examples. That is, my invention,

mesa-sci as hereinafter pointed out, although supplying armor plate of the highest grade, is also applicable under modified analyses and heat treatment to the softer classes of steels such as are commonly used in the manufacture of machine parts such as crank shafts and the like.

By my invention, I am enabled to pro-' duce a steel which may be termed a zirconium steel, which is characterized by possessing, in a marked degree, physical properties and combinations of properties such as hereinbefore set forth, of an excellence which has hitherto seldom been attained in the fabrication of steel and steel products. In carrying out my invention It add airconium to the usual elements constituting v what is usually termed steel, as determined by the requirements of-the particular field of use, in quantities at least sufiicient to produce a product containing zirconium from a substantial fraction of one-tenth of one per cent to not materially more than one per cent, altho for certain special purposes it may be desirable to carry the percentage higher. These percentages appear conium in the finished product under conditions which I will point out even in extremely small quantities, such as .04 to .08 of one per cent, produces marked etlects as will appear.

to be notably low, but the presence of zir- In the penodic system of classification of the elements,. zirconium is placed in the group containing carbon,"silicon and titanium, indicating that it possesses chemical and hence metallurgical properties and characteristics similar to those of these elements. ll am aware that it has been suggested, as for example in the United States Letters Patent byWeiss No. 982,326, to use zirconium in the manufacture of castings and the like as a deoxidizing substance adapted to produce sound castings, in which respect zirconium has an action closely akin to that of titanium; and that as thus employed it has the efiect of increasing certain of the properties of the metal as might be expected from the use of any satisfactory deoxidizing agent. ll'do not, however, propose to make use of those deoxidizing characteristics which may be described as being analogous to titanium, but to take advantage of those characteristics which may be described as being analogous to those of carbon and silicon. Steels produced by my invcntioii are true zirconium steels in contrast with steels merely deoxidized by that element and which might contain small amounts of zirconium included in the metalas an inert slag. For example: In certain classes of my steelsone effect of the added zirconium will in the annealed or normalized state be evidenced a microscopically visible change in the appearance of the normal L'Ihe: zirconium in this e of steel behaves in a' manner similar to car 11;

in other types the element remains substantially in solid solution and affects the properties of the steel indirectly, when its action is comparable to the behavior of silicon. In other words, in some cases I replacepart of the carbon of the usual steels by zirconium and thereby secure after roper heat treatment a steel possessing a com ination of physical properties well in advance of those of the corresponding carbon steel; likewise I in other cases, I replace silicon by zirconium and heat treatment obtain a zirconium steel or a zlrcomum-silicon steel having a combination of the special properties of silicon steels and indivi ually in excess thereof without the corresponding difiiculties involved in the corresponding in- These zirconium steels over the corth in the matter crease in silicon. therefore have advanta responding silicon steels .of ultimate physical properties and in various steps involved-in manufacture and pro duction I add the zirconium in a form which is soluble in the liquid and either partially or wholly solublein the solid state of the steel, and for this purpose I prefer to employ an allo or com ound of zirconium low'in'carbon, together with iron, nickel, cobalt, cop-.

or silicon 'm esium aluminum manganese, or titanium either singly or in combination, large percentages .of zirconium. It is desirable that an element having a greater chemical affinity for oxygen, such as aluminum or magnesium, be

resent in the alloy for by this means comp etedeoxidation of the steel is eflectedwithout a correspondingilossmf zirconium. If the steel to produced is to beef the tungsten, chromium, molybdenumor vanadium types, the zirconium alloy may contain the these elements with advantages as they increase the specific avityan somewhat aid the absorptiogi of t thesteel.

I have found the following alloys. to suc-' cessfully serve the purpose:

1 Such alloys may, be made by the Goldschmidt reaction or reduced in'the electric furnace, or

.a combination of these methodsmay be used.

The" amount of the alloy to be added in art or all of theconium on the v trated in the fa lowing comparative tables.

which contaims, comparativelyw uired amounts of e. corresponding alloy'by.

zirconium is dependent upon. itsanalysis.

and the analysis temperature, and. state of deoxldation of the steel. For example, al-

loys'high in aluminum are'lighter' than the molten steel and it is difficult to efiect their complete solution, and alloys containing a .high percentage of carbon tend to slag off part of the zirconium carbide. A badly oxidized steel bath will slag off the zirconium aszirconiu'm-oxide. I prefer to add the zirconium in the furnace just previous to pouring the steel, after deox'idation and under a neutral or slightly acid slag. Zirconium alloys of low melting point, such as the nickel-silicon types, may be added in the ladle.

The specific effects of the resence roperties o of zir- E'spe'cially are they to be derived when the zirconium is used in combination with nickel, and I have chosen steels of this, type as examples for purposes of illustration? These four steels were'all poured from the -same.heat of steel by successively tapping steel is illusthe furnace after increasing zirconium additions The ingotswere forged and the test bars from'them were heat treated under as nearly like conditions as possible.

Analyses. l

"(Iron-in oath liratance'forming balance ot the .PPFZ; assss man Heat ltz'eatmw-fize f ple trefe t eci (2) 11560 degrees F.,'. hold at temperature IO minutes, quench in 011. v p

(3) 880 degrees F., hold' ,at temperature 2 hours air'cool." Standard test bars made and tested with the following results:.

1 I m ma properties.

No. 2. No. 4".

of .505 diam." were Steel of the shown by .the analysis 6r ingot'#1 above, though containing no"zir-. conium, is in itself an excellent material for order to secure the required percentage of armor plate. and as such has 'found wide use. The marked betterment of all the physical properties producedv by the pres ence of the zirconium is therefore of great benefit to the manufacturer for it permits him a wider range of manufacturing practice without exceeding the limits of hardness and toughness required and hence a greater manufacturing and ballistic yield...

Attention is, especially called to the extremely higlrreduction in area corresponding with the tensile strength andhardness.

is a factor of prime importance in armor plate, springs, dies, and the like.

The results obtained in armor plate steel roduced in accordance with my invention is illustrated in the following silico-nickel manganese steel in which part of the silicon is replaced by the element zirconium; a

plate seven inches in diameter and having an average thickness of .34: inch was forged from a steel of the following analys15:

Carbon 0. 38 Nickel 3.20 Silicon 0. 88 Manganese 0. 75 Zirconium 04,10 Sulphur 0. 033 Phosphorus 0.018

Iron-balance of the 100% It was then heated to 1000 degrees F. and cooled in mica dust, reheated to 1560 degrees R, which is slightly beyond the critical range and quenched in oil and finally drawn at 37 5 degrees F. for two hours. This treatment yielded a fine martensitic structure.

The nature and results of the ballistic In all the above the line of fire'was at ri ht angles to the surface of the plate. he plate resisted all shots" without penetration or fracture. A slight indentation was caused by the cutting action of the projec:

narrator tile and in the case of shots-number four and number five the plate slightly bulged at the point of import.

lit will be seen that the plate, altho approximately only one half the regulation .05" these conditions, withstood under standard conditions the firingof a gun having a muzzle velocity and consequently an impacting force far greater than that of the gun used in standard testing practice. This advance not only meets the requirements for armor plate intended for ordinary uses, but also provides a weight and strength adapted for the needs of aeroplane protection, for body armor and for the protection of light, mobile implements generally.

Physical tests on bars cut from this plate gave the following results:

Brinnell hardness. 578 Sclerescope hardness 78.85 Tensile strength 286,000 Elastic limit -f 280,000 Bed in area 1 35% Elongation 10.15% Angle of cold bend 25 degrees Specimen .34 60"4-6 The above physical properties afiord the explanation of the results noted on the ballistic test. It will be observed that the hard-- ness was suficient when coupled with the elastic limit, to shatter the projectile; the

toughness, as measured by the mean breaknag strength and the reductionin area, was

suthcieiat to prevent the local punching out.

(important consideration in thin plate);

and the toughness, as measured by the elongation and mean breaking strength and indicated by the angle of cold bend, was sulficient to prevent fracture and breaking. For armor plate up to .65 inch in thickness ll prefer the following analysis:

Garbon 38-.46 Nickel 2.72-3.50 Silicon 1204.50 Zirconium 10-140 Manganese 80-100 Sulphur 035 max. Phosphorous -035 max.

Balance iron.

For thicker plates the addition of 30% molybdenum or its equivalent in chromium or tungsten or approximately 35% cobalt is desirable to increase the hardening properties. Two tenths of one per cent vanadh' um may also be added .with advantage. Such a steel is readily capable of rolling into thin sheets (e. g. .20" 0 and gives excellent properties upon oil hardening.

While the examples given only illustrate the effect of zirconium on a silicon steel, nevertheless its similarity to carbon is such that itmay be substituted in small-quanthickness which is permitted under I llld tities for that element, as for example in the chrome steels and chrome nickel steels, with results similar to those given. Furthermore,

such zirconium steels may be modified-by the additions of molybdenum, cobalt, tung-" sten, vanadium and other alloys to increase certain of their physical properties for special uses in a manner familiar to those chining operations other than grinding af-' I ter the heat treatment. However, with suitable modifications in analysis and heattreatment, such as the use .of smaller percentage of carbon and higher drawing temratures, steels of the softer and more read- 11y machinable types may-be produced and, because of the excellence oftheir physical properties, ready work abilit and cost of manufacture are especially sultable for gen- .eral forgings for machine parts such as pirignkshafts, axles, connecting rods and the For example: a steel of the following .-analysis- 7 Per cent C 32 -M n I jSi Ni 2.75 s 018 P 020 Zr 22 Iron-balance.

- when heat treated as follows on a 1'. section:

I the following physical properties:

Elongation 17% Red area 54% Brinnell s 302% Elastic limit (1) 1600 degrees F. ai r cool; v(2) 1560 degrees F. up to heat 10. minutes, quench in oil; (3) 1050 degrees F. anneal 2 hrs. gave Tensile strength 156,000 lbsQper in. 155,200 lbs. per sq. in.

indicated by the subjoined. claims.

Owing to the small (percentages used a and the comparative abun ance and cheapness,

zirconium steels of extraordinary quality may be manufactured according to 'my in- .vention at a far less. cost than by means. of

the usual alloys em loyed in steel manufacture such as vana ium, tungsten, etc.

. or pearhte.

to one per cent.

I one per cent by Wu I claim I 1. Heat treated alloy steel including the usual constituents thatgo'to make up'steeland less than one per cent of zirconium as an added element.

2. A steel containing zirconium as an added element and characterized in. the finished stateby a substantially solidsolution of zirconium pearlite which appears with the usual pearlite or ferrite in the steel in the annealed state. L

3. Heat treated alloy steel containing less than one per cent of zirconium.

4. Alloy steel including the usual con- 'stituents' that go to make up .steeland embodying zirconium in an amount be ween substantially one tenth of'one per weight and substantially one per cent by weight.

5. Heat treated alloy steel suitable for use in thin sheets as armor plate and having. a high ballistic yield when so applied,

and embodying zirconium in quantities between .04 per cent and substantially one 'per cent by weight.

6. A steel for producing articles-"to be heat treated, said steel containing-zirconium as an added element and beiiig characterized in the annealed or normalized state by microscopically visible zirconium eutectic 7. Steel embodying less than one per cent of zirconium which steel has been heated to within the critical range.

steel, the addi- 8. In he manufacture of .tion of zirconium in a form which issoluble in the metal in the liquid stateand partly or wholly; soluble in the metal in the solid State. i

9. In the manufacture of steel, the addition' of zirconium in a state" which will form a zirconium compound which is soluble in the metal. in the liquid state and wholly or partly soluble in the metal in the solid state.

of the carbon is replaced by less than one per cent of the elementflzirconium.

11. Armor plate including the usual constituents that go to make u steel and emp I .10. A heat treated steel in which a part bodying zirc'omuni as an a dedleleinent up 12. Armor plate 7 yield and. containing the usual constituents that go to make up steel and embodying.-

having a high'ballisti to substantially T ingthe usual iugradients and zirecpnium as an added element in an efi'ective amount; up to substantially 1 per cent.

15. Forged alley steel containing zircon- 5 ium in an ufi'ective amount up to subsisan tially 1%.

16.8% ambodying zirconium in an effective amount up 'to substantiafiy 1%,

which steel has been mechanically worked while hat.

17, A110 steel including the'usual constitueuts t at. g0 to make upsteul and embodyiug zirconium in an efiectiva amount up ta substantially 1%.

HENRY T. @HANDLER. 

